The invention pertains to switchable circuit devices, and methods of forming switchable devices. In particular applications, the invention pertains to semiconductor constructions comprising switchable circuit devices.
Various molecular switches have been developed within the past several years. The molecular switches are characterized by having two stable states which can be interchanged with one another. Exemplary molecular switches include redox-active catenanes, redox-active rotaxanes, and redox-active pseudorotaxanes. The molecular switches can be, for example, materials which can be interchanged between two stable states by oxidation and reduction. The oxidation and reduction of a material can be accomplished by, for example, altering a voltage that the material is exposed to.
In referring to this disclosure and the claims which follow, a preferred exemplary switchable material is referred to as a xe2x80x9cmolecular switchable memory materialxe2x80x9d, with the term xe2x80x9cmemoryxe2x80x9d emphasizing that the material has at least two stable and interchangeable states. It is possible that a memory material can have more than two stable states, but generally it is preferred that the material have only two stable states accessible in the particular environment that the material is utilized in. For instance, a material having multiple stable states accessible through redox reactions can be utilized in an environment wherein a voltage to the material is controlled such that only two of the stable states are accessed during utilization of the material as an active molecular switch.
In theory, the molecular switches can be incorporated into switchable circuit devices. Specifically, one of the stable states of a molecular switch can be referred to as a xe2x80x9c1xe2x80x9d digital state, and the other stable state can be referred to as a xe2x80x9c0xe2x80x9d. Accordingly, a circuit device comprising a molecular switch material can be switchable between a first state corresponding to the xe2x80x9c0xe2x80x9d and a second state corresponding to the xe2x80x9c1xe2x80x9d. The two states can be utilized for storing memory bits. Additionally, and/or alternatively, one of the stable states of a switchable molecular material can be referred to as an xe2x80x9con statexe2x80x9d and the other as an xe2x80x9coff state,xe2x80x9d and the material can be utilized to control electrical flow within a circuit. Specifically, when the material is in the xe2x80x9con statexe2x80x9d electrical flow can proceed through the circuit, and when the material is switched to the xe2x80x9coff statexe2x80x9d, electrical flow can be stopped within the circuit.
Various difficulties are encountered in attempting to incorporate that the switchable molecular material can be destroyed when incorporated into the circuit, and accordingly will no longer act as a molecular switch. For purposes of interpreting this disclosure and the claims that follow, an xe2x80x9cactivexe2x80x99 molecular switch is defined as a molecule which retains an ability to switch from one stable state to another.
It would be desirable to develop new circuit structures incorporating molecular switches, and to develop new methods of forming circuit structures comprising molecular switches.
In one aspect, the invention encompasses a method of forming a switchable circuit device. A mass is formed over a substrate, and while the mass is over the substrate pores are formed within the mass to convert the mass to a porous matrix. An active molecular switchable memory material is provided within the pores of the porous matrix. An electrical connection is formed to the porous matrix.
In another aspect, the invention encompasses a method wherein a first conductive wiring layer is formed to be supported by semiconductor substrate. Porous silicon is formed over the conductive wiring layer, and an active molecular switchable memory material is formed within pores of the porous silicon. A second conductive wiring layer is formed over the porous silicon.
In one aspect, the invention encompasses a switchable circuit device comprising a porous silicon matrix and an active molecular switchable memory material within the porous silicon matrix.
In one aspect, the invention encompasses a switchable circuit device comprising a first conductive layer and a porous silicon matrix over the first conductive layer. A material is dispersed within pores of the porous silicon matrix, and the material has two stable states. A second conductive layer is formed over the porous silicon matrix. A current flow between the first and second conductive layers is influenced by which of the stable states the material is in.